基于单片机技术的火花塞离子电流检测系统研究

Study on Spark Plug Ion Current Detecting System Based on SCM Technology

基于离子电流的诊断方法,设计了一套以火花塞为传感器,以MC9S12XS128单片机为核心的离子电流检测系统.该系统应用单片机技术以及离子电流回路检测发动机工作时的燃烧信号,通过高压硅堆以及小波降噪技术自动隔离高压、高频信号,然后对火花塞离子电流信号进行在线采集并通过界面显示,有效提取特征参数;对发动机运行过程中离子电流信号进行试验研究,采集1 000个点耗时约20 259μs,离子电流两个峰值之间的时间间隔大约为5 ms,此离子电流的峰值延迟时刻大约是42°,与实际气缸的燃烧情况基本一致;通过与数字示波器采集信号对比,验证了本系统对离子电流信号采集的准确性.

Based on the diagnosis method of ion current, a new ionic current detection system was designed, which included spark plug that was used as the sensor directly and MC9S12 series of high performance micro- controller that was the core control unit. The signal of engine combustion was detected by microcontroller and ion current loop, and the signals could be online acquired and revealed through the interface, by isolating highvoltage, high-frequency signal automatically with the high-voltage silicon stack and wavelet deoising tech- nique. Then the state parameters could be distilled effectively. The ionic current signal during engine operation was investigated in the experiment. It took about 20 259μs and acquisition 1 000 point. Two peak of ion current interval is about 5ms. The late timing of the ion current peak is about 42°, consistent with the combustion situation of the actual cylinder. It is concluded that the system is accurate in the ion current acquisition by compared with oscilloscope （OSC） acquisition.